Fix encoded header signing. (#765)

The header needs to be properly formatted so that Unicode characters are encoded the same way they will be in the final message. Previously the logical header value was being encoded.

A notable example is that a `'` in the `To:` header needs to be encoded. This was being encoded incorrectly.

src/message/dkim.rs

@@ -1,14 +1,14 @@
 use std::{
     borrow::Cow,
     error::Error as StdError,
-    fmt::{self, Display, Write},
+    fmt::{self, Display},
     iter::IntoIterator,
     time::SystemTime,
 };
 
 use ed25519_dalek::Signer;
 use once_cell::sync::Lazy;
-use regex::{bytes::Regex as BRegex, Regex};
+use regex::bytes::Regex;
 use rsa::{pkcs1::DecodeRsaPrivateKey, Hash, PaddingScheme, RsaPrivateKey};
 use sha2::{Digest, Sha256};
 
@@ -222,9 +222,9 @@ fn dkim_canonicalize_body(
     body: &[u8],
     canonicalization: DkimCanonicalizationType,
 ) -> Cow<'_, [u8]> {
-    static RE: Lazy<BRegex> = Lazy::new(|| BRegex::new("(\r\n)+$").unwrap());
-    static RE_DOUBLE_SPACE: Lazy<BRegex> = Lazy::new(|| BRegex::new("[\\t ]+").unwrap());
-    static RE_SPACE_EOL: Lazy<BRegex> = Lazy::new(|| BRegex::new("[\t ]\r\n").unwrap());
+    static RE: Lazy<Regex> = Lazy::new(|| Regex::new("(\r\n)+$").unwrap());
+    static RE_DOUBLE_SPACE: Lazy<Regex> = Lazy::new(|| Regex::new("[\\t ]+").unwrap());
+    static RE_SPACE_EOL: Lazy<Regex> = Lazy::new(|| Regex::new("[\t ]\r\n").unwrap());
     match canonicalization {
         DkimCanonicalizationType::Simple => RE.replace(body, &b"\r\n"[..]),
         DkimCanonicalizationType::Relaxed => {
@@ -241,23 +241,59 @@ fn dkim_canonicalize_body(
     }
 }
 
-/// Canonicalize the value of an header
-fn dkim_canonicalize_header_value(
-    value: &str,
-    canonicalization: DkimCanonicalizationType,
-) -> Cow<'_, str> {
-    match canonicalization {
-        DkimCanonicalizationType::Simple => Cow::Borrowed(value),
-        DkimCanonicalizationType::Relaxed => {
-            static RE_EOL: Lazy<Regex> = Lazy::new(|| Regex::new("\r\n").unwrap());
-            static RE_SPACES: Lazy<Regex> = Lazy::new(|| Regex::new("[\\t ]+").unwrap());
-            let value = RE_EOL.replace_all(value, "");
-            Cow::Owned(format!(
-                "{}\r\n",
-                RE_SPACES.replace_all(&value, " ").trim_end()
-            ))
+fn dkim_canonicalize_headers_relaxed(headers: &str) -> String {
+    let mut r = String::with_capacity(headers.len());
+
+    fn skip_whitespace(h: &str) -> &str {
+        match h.as_bytes().get(0) {
+            Some(b' ' | b'\t') => skip_whitespace(&h[1..]),
+            _ => h,
         }
     }
+
+    fn name(h: &str, out: &mut String) {
+        if let Some(name_end) = h.bytes().position(|c| c == b':') {
+            let (name, rest) = h.split_at(name_end + 1);
+            *out += name;
+            // Space after header colon is stripped.
+            value(skip_whitespace(rest), out);
+        } else {
+            // This should never happen.
+            *out += h;
+        }
+    }
+
+    fn value(h: &str, out: &mut String) {
+        match h.as_bytes() {
+            // Continuation lines.
+            [b'\r', b'\n', b' ' | b'\t', ..] => {
+                out.push(' ');
+                value(skip_whitespace(&h[2..]), out);
+            }
+            // End of header.
+            [b'\r', b'\n', ..] => {
+                *out += "\r\n";
+                name(&h[2..], out)
+            }
+            // Sequential whitespace.
+            [b' ' | b'\t', b' ' | b'\t' | b'\r', ..] => value(&h[1..], out),
+            // All whitespace becomes spaces.
+            [b'\t', ..] => {
+                out.push(' ');
+                value(&h[1..], out)
+            }
+            [_, ..] => {
+                let mut chars = h.chars();
+                out.push(chars.next().unwrap());
+                value(chars.as_str(), out)
+            }
+            [] => {}
+        }
+    }
+
+    name(headers, &mut r);
+
+    r
 }
 
 /// Canonicalize header tag
@@ -277,47 +313,35 @@ fn dkim_canonicalize_headers<'a>(
     mail_headers: &Headers,
     canonicalization: DkimCanonicalizationType,
 ) -> String {
+    let mut covered_headers = Headers::new();
+    for name in headers_list {
+        if let Some(h) = mail_headers.find_header(name) {
+            let name = dkim_canonicalize_header_tag(name, canonicalization);
+            covered_headers.insert_raw(HeaderValue::dangerous_new_pre_encoded(
+                HeaderName::new_from_ascii(name.into()).unwrap(),
+                h.get_raw().into(),
+                h.get_encoded().into(),
+            ));
+        }
+    }
+
+    let serialized = covered_headers.to_string();
+
     match canonicalization {
-        DkimCanonicalizationType::Simple => {
-            let mut signed_headers = Headers::new();
-
-            for h in headers_list {
-                let h = dkim_canonicalize_header_tag(h, canonicalization);
-                if let Some(value) = mail_headers.get_raw(&h) {
-                    signed_headers.insert_raw(HeaderValue::new(
-                        HeaderName::new_from_ascii(h.into()).unwrap(),
-                        dkim_canonicalize_header_value(value, canonicalization).to_string(),
-                    ))
-                }
-            }
-
-            signed_headers.to_string()
-        }
-        DkimCanonicalizationType::Relaxed => {
-            let mut signed_headers = String::new();
-
-            for h in headers_list {
-                let h = dkim_canonicalize_header_tag(h, canonicalization);
-                if let Some(value) = mail_headers.get_raw(&h) {
-                    write!(
-                        signed_headers,
-                        "{}:{}",
-                        h,
-                        dkim_canonicalize_header_value(value, canonicalization)
-                    )
-                    .expect("write implementation returned an error")
-                }
-            }
-
-            signed_headers
-        }
+        DkimCanonicalizationType::Simple => serialized,
+        DkimCanonicalizationType::Relaxed => dkim_canonicalize_headers_relaxed(&serialized),
     }
 }
 
 /// Sign with Dkim a message by adding Dkim-Signture header created with configuration expressed by
 /// dkim_config
-pub(super) fn dkim_sign(message: &mut Message, dkim_config: &DkimConfig) {
-    let timestamp = SystemTime::now()
+
+pub fn dkim_sign(message: &mut Message, dkim_config: &DkimConfig) {
+    dkim_sign_fixed_time(message, dkim_config, SystemTime::now())
+}
+
+fn dkim_sign_fixed_time(message: &mut Message, dkim_config: &DkimConfig, timestamp: SystemTime) {
+    let timestamp = timestamp
         .duration_since(SystemTime::UNIX_EPOCH)
         .unwrap()
         .as_secs();
@@ -385,21 +409,44 @@ pub(super) fn dkim_sign(message: &mut Message, dkim_config: &DkimConfig) {
 
 #[cfg(test)]
 mod test {
-    use std::{
-        io::Write,
-        process::{Command, Stdio},
-    };
-
     use super::{
         super::{
             header::{HeaderName, HeaderValue},
             Header, Message,
         },
-        dkim_canonicalize_body, dkim_canonicalize_header_value, dkim_canonicalize_headers,
+        dkim_canonicalize_headers, dkim_sign_fixed_time, DkimCanonicalization,
         DkimCanonicalizationType, DkimConfig, DkimSigningAlgorithm, DkimSigningKey,
     };
     use crate::StdError;
 
+    const KEY_RSA: &str = "-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----";
+
     #[derive(Clone)]
     struct TestHeader(String);
 
@@ -417,47 +464,11 @@ mod test {
         }
     }
 
-    #[test]
-    fn test_body_simple_canonicalize() {
-        let body = b"test\r\n\r\ntest   \ttest\r\n\r\n\r\n";
-        let expected: &[u8] = b"test\r\n\r\ntest   \ttest\r\n";
-        assert_eq!(
-            dkim_canonicalize_body(body, DkimCanonicalizationType::Simple),
-            expected
-        )
-    }
-    #[test]
-    fn test_body_relaxed_canonicalize() {
-        let body = b"test\r\n\r\ntest   \ttest\r\n\r\n\r\n";
-        let expected: &[u8] = b"test\r\n\r\ntest test\r\n";
-        assert_eq!(
-            dkim_canonicalize_body(body, DkimCanonicalizationType::Relaxed),
-            expected
-        )
-    }
-    #[test]
-    fn test_header_simple_canonicalize() {
-        let value = "test\r\n\r\ntest   \ttest\r\n";
-        let expected = "test\r\n\r\ntest   \ttest\r\n";
-        assert_eq!(
-            dkim_canonicalize_header_value(value, DkimCanonicalizationType::Simple),
-            expected
-        )
-    }
-    #[test]
-    fn test_header_relaxed_canonicalize() {
-        let value = "test\r\n\r\ntest   \ttest\r\n";
-        let expected = "testtest test\r\n";
-        assert_eq!(
-            dkim_canonicalize_header_value(value, DkimCanonicalizationType::Relaxed),
-            expected
-        )
-    }
-
     fn test_message() -> Message {
         Message::builder()
-            .from("Test <test+ezrz@example.net>".parse().unwrap())
+            .from("Test O'Leary <test+ezrz@example.net>".parse().unwrap())
             .to("Test2 <test2@example.org>".parse().unwrap())
+            .date(std::time::UNIX_EPOCH)
             .header(TestHeader("test  test very very long with spaces and extra spaces   \twill be folded to several lines ".to_string()))
             .subject("Test with utf-8 ë")
             .body("test\r\n\r\ntest   \ttest\r\n\r\n\r\n".to_string()).unwrap()
@@ -466,63 +477,121 @@ mod test {
     #[test]
     fn test_headers_simple_canonicalize() {
         let message = test_message();
-        assert_eq!(dkim_canonicalize_headers(["From", "Test"], &message.headers, DkimCanonicalizationType::Simple),"From: Test <test+ezrz@example.net>\r\nTest: test  test very very long with spaces and extra spaces   \twill be \r\n folded to several lines \r\n")
+        dbg!(message.headers.to_string());
+        assert_eq!(dkim_canonicalize_headers(["From", "Test"], &message.headers, DkimCanonicalizationType::Simple), "From: =?utf-8?b?VGVzdCBPJ0xlYXJ5?= <test+ezrz@example.net>\r\nTest: test  test very very long with spaces and extra spaces   \twill be \r\n folded to several lines \r\n")
     }
+
     #[test]
     fn test_headers_relaxed_canonicalize() {
         let message = test_message();
-        assert_eq!(dkim_canonicalize_headers(["From", "Test"], &message.headers, DkimCanonicalizationType::Relaxed),"from:Test <test+ezrz@example.net>\r\ntest:test test very very long with spaces and extra spaces will be folded to several lines\r\n")
+        dbg!(message.headers.to_string());
+        assert_eq!(dkim_canonicalize_headers(["From", "Test"], &message.headers, DkimCanonicalizationType::Relaxed),"from:=?utf-8?b?VGVzdCBPJ0xlYXJ5?= <test+ezrz@example.net>\r\ntest:test test very very long with spaces and extra spaces will be folded to several lines\r\n")
     }
+
     #[test]
-    fn test_signature_rsa() {
+    fn test_signature_rsa_simple() {
         let mut message = test_message();
-        let key = "-----BEGIN RSA PRIVATE KEY-----
-MIIEpAIBAAKCAQEAz+FHbM8BwkBBz/Ux5OYLQ5Bp1HVuCHTP6Rr3HXTnome/2cGl
-/ze0tsmmFbCjjsS89MXbMGs9xJhjv18LmL1N0UTllblOizzVjorQyN4RwBOfG34j
-7SS56pwzrA738Ry8FAbL5InPWEgVzbOhXuTCs8yuzcqTnm4sH/csnIl7cMWeQkVn
-1FR9LKMtUG0fjhDPkdX0jx3qTX1L3Z7a7gX6geY191yNd9i9DvE2/+wMigMYz1LA
-ts4alk2g86MQhtbjc8AOR7EC15hSw37/lmamlunYLa3wC+PzHNMA8sAfnmkgNvip
-ssjh8LnelD9qn+VtsjQB5ppkeQx3TcUPvz5z+QIDAQABAoIBAQCzRa5ZEbSMlumq
-s+PRaOox3CrIRHUd6c8bUlvmFVllX1++JRhInvvD3ubSMcD7cIMb/D1o5jMgheMP
-uKHBmQ+w91+e3W30+gOZp/EiKRDZupIuHXxSGKgUwZx2N3pvfr5b7viLIKWllpTn
-DpCNy251rIDbjGX97Tk0X+8jGBVSTCxtruGJR5a+hz4t9Z7bz7JjZWcRNJC+VA+Q
-ATjnV7AHO1WR+0tAdPJaHsRLI7drKFSqTYq0As+MksZ40p7T6blZW8NUXA09fJRn
-3mP2TZdWjjfBXZje026v4T7TZl+TELKw5WirL/UJ8Zw8dGGV6EZvbfMacZuUB1YQ
-0vZnGe4BAoGBAO63xWP3OV8oLAMF90umuusPaQNSc6DnpjnP+sTAcXEYJA0Sa4YD
-y8dpTAdFJ4YvUQhLxtbZFK5Ih3x7ZhuerLSJiZiDPC2IJJb7j/812zQQriOi4mQ8
-bimxM4Nzql8FKGaXMppE5grFLsy8tw7neIM9KE4uwe9ajwJrRrOTUY8ZAoGBAN7t
-+xFeuhg4F9expyaPpCvKT2YNAdMcDzpm7GtLX292u+DQgBfg50Ur9XmbS+RPlx1W
-r2Sw3bTjRjJU9QnSZLL2w3hiii/wdaePI4SCaydHdLi4ZGz/pNUsUY+ck2pLptS0
-F7rL+s9MV9lUyhvX+pIh+O3idMWAdaymzs7ZlgfhAoGAVoFn2Wrscmw3Tr0puVNp
-JudFsbt+RU/Mr+SLRiNKuKX74nTLXBwiC1hAAd5wjTK2VaBIJPEzilikKFr7TIT6
-ps20e/0KoKFWSRROQTh9/+cPg8Bx88rmTNt3BGq00Ywn8M1XvAm9pyd/Zxf36kG9
-LSnLYlGVW6xgaIsBau+2vXkCgYAeChVdxtTutIhJ8U9ju9FUcUN3reMEDnDi3sGW
-x6ZJf8dbSN0p2o1vXbgLNejpD+x98JNbzxVg7Ysk9xu5whb9opC+ZRDX2uAPvxL7
-JRPJTDCnP3mQ0nXkn78xydh3Z1BIsyfLbPcT/eaMi4dcbyL9lARWEcDIaEHzDNsr
-NlioIQKBgQCXIZp5IBfG5WSXzFk8xvP4BUwHKEI5bttClBmm32K+vaSz8qO6ak6G
-4frg+WVopFg3HBHdK9aotzPEd0eHMXJv3C06Ynt2lvF+Rgi/kwGbkuq/mFVnmYYR
-Fz0TZ6sKrTAF3fdkN3bcQv6JG1CfnWENDGtekemwcCEA9v46/RsOfg==
------END RSA PRIVATE KEY-----";
-        let signing_key = DkimSigningKey::new(key, DkimSigningAlgorithm::Rsa).unwrap();
-        message.sign(&DkimConfig::default_config(
-            "dkimtest".to_string(),
-            "example.org".to_string(),
-            signing_key,
-        ));
-        println!("{}", std::str::from_utf8(&message.formatted()).unwrap());
-        let mut verify_command = Command::new("dkimverify")
-            .stdin(Stdio::piped())
-            .spawn()
-            .expect("Fail to verify message signature");
-        let mut stdin = verify_command.stdin.take().expect("Failed to open stdin");
-        std::thread::spawn(move || {
-            stdin
-                .write_all(&message.formatted())
-                .expect("Failed to write to stdin");
-        });
-        assert!(verify_command
-            .wait()
-            .expect("Command did not run")
-            .success());
+        let signing_key = DkimSigningKey::new(KEY_RSA, DkimSigningAlgorithm::Rsa).unwrap();
+        dkim_sign_fixed_time(
+            &mut message,
+            &DkimConfig::new(
+                "dkimtest".to_string(),
+                "example.org".to_string(),
+                signing_key,
+                vec![
+                    HeaderName::new_from_ascii_str("Date"),
+                    HeaderName::new_from_ascii_str("From"),
+                    HeaderName::new_from_ascii_str("Subject"),
+                    HeaderName::new_from_ascii_str("To"),
+                ],
+                DkimCanonicalization {
+                    header: DkimCanonicalizationType::Simple,
+                    body: DkimCanonicalizationType::Simple,
+                },
+            ),
+            std::time::UNIX_EPOCH,
+        );
+        let signed = message.formatted();
+        let signed = std::str::from_utf8(&signed).unwrap();
+        assert_eq!(
+            signed,
+            std::concat!(
+                "From: =?utf-8?b?VGVzdCBPJ0xlYXJ5?= <test+ezrz@example.net>\r\n",
+                "To: Test2 <test2@example.org>\r\n",
+                "Date: Thu, 01 Jan 1970 00:00:00 +0000\r\n",
+                "Test: test  test very very long with spaces and extra spaces   \twill be \r\n",
+                " folded to several lines \r\n",
+                "Subject: Test with utf-8 =?utf-8?b?w6s=?=\r\n",
+                "Content-Transfer-Encoding: 7bit\r\n",
+                "DKIM-Signature: v=1; a=rsa-sha256; d=example.org; s=dkimtest; \r\n",
+                " c=simple/simple; q=dns/txt; t=0; h=Date:From:Subject:To; \r\n",
+                " bh=f3Zksdcjqa/xRBwdyFzIXWCcgP7XTgxjCgYsXOMKQl4=; b=UQWpUooKjVzgC7jtuEKdpCbz\r\n",
+                " sSDnOqZFg8+S7rZj89n/+AVsdcwxumeLCUYLeko2TZgVFJA7kGz+wLzH2wpzB4XnyUqrkF6PrFA\r\n",
+                " 9K11K365JDtzfMSc5eRVS8crO6F/A9QtXPndnzrXQ5HrtFgfxUlJ9cX6pTOor1NVCpfYUNBviIg\r\n",
+                " Am0LnUOKdlJ8z82kLFRpIqawMKNVfyqP8Es6H3NHM4Y1uwGgls9DM1+lZxNXxkMpoGV3rL/n/ai\r\n",
+                " s8+VifrRxPLB0mr9gbavSkCQ2QzUA/+iq8DgPCGpXDrdDrwTcrV3pL/iHyEjQZWwFSQkx+r/CGb\r\n",
+                " 8TQLqH6T3wfr69XWvg==\r\n",
+                "\r\n",
+                "test\r\n",
+                "\r\n",
+                "test   \ttest\r\n",
+                "\r\n",
+                "\r\n",
+            )
+        );
+    }
+
+    #[test]
+    fn test_signature_rsa_relaxed() {
+        let mut message = test_message();
+        let signing_key = DkimSigningKey::new(KEY_RSA, DkimSigningAlgorithm::Rsa).unwrap();
+        dkim_sign_fixed_time(
+            &mut message,
+            &DkimConfig::new(
+                "dkimtest".to_string(),
+                "example.org".to_string(),
+                signing_key,
+                vec![
+                    HeaderName::new_from_ascii_str("Date"),
+                    HeaderName::new_from_ascii_str("From"),
+                    HeaderName::new_from_ascii_str("Subject"),
+                    HeaderName::new_from_ascii_str("To"),
+                ],
+                DkimCanonicalization {
+                    header: DkimCanonicalizationType::Relaxed,
+                    body: DkimCanonicalizationType::Relaxed,
+                },
+            ),
+            std::time::UNIX_EPOCH,
+        );
+        let signed = message.formatted();
+        let signed = std::str::from_utf8(&signed).unwrap();
+        println!("{}", signed);
+        assert_eq!(
+            signed,
+            std::concat!(
+                "From: =?utf-8?b?VGVzdCBPJ0xlYXJ5?= <test+ezrz@example.net>\r\n",
+                "To: Test2 <test2@example.org>\r\n",
+                "Date: Thu, 01 Jan 1970 00:00:00 +0000\r\n",
+                "Test: test  test very very long with spaces and extra spaces   \twill be \r\n",
+                " folded to several lines \r\n",
+                "Subject: Test with utf-8 =?utf-8?b?w6s=?=\r\n",
+                "Content-Transfer-Encoding: 7bit\r\n",
+                "DKIM-Signature: v=1; a=rsa-sha256; d=example.org; s=dkimtest; \r\n",
+                " c=relaxed/relaxed; q=dns/txt; t=0; h=date:from:subject:to; \r\n",
+                " bh=qN8je6qJgWFGSnN2MycC/XKPbN6BOrMJyAX2h4m19Ss=; b=YaVfmH8dbGEywoLJ4uhbvYqD\r\n",
+                " yQG1UGKFH3PE7zXGgk+YFxUgkwWjoA3aQupDNQtfTjfUsNe0dnrjyZP+ylnESpZBpbCIf5/n3FE\r\n",
+                " h6j3RQthqNbQblcfH/U8mazTuRbVjYBbTZQDaQCMPTz+8D+ZQfXo2oq6dGzTuGvmuYft0CVsq/B\r\n",
+                " Ip/EkhZHqiphDeVJSHD4iKW8+L2XwEWThoY92xOYc1G0TtBwz2UJgtiHX2YulH/kRBHeK3dKn9R\r\n",
+                " TNVL3VZ+9ZrnFwIhET9TPGtU2I+q0EMSWF9H9bTrASMgW/U+E0VM2btqJlrTU6rQ7wlQeHdwecL\r\n",
+                " nzXcyhCUInF1+veMNw==\r\n",
+                "\r\n",
+                "test\r\n",
+                "\r\n",
+                "test   \ttest\r\n",
+                "\r\n",
+                "\r\n",
+            )
+        );
     }
 }

src/message/header/mod.rs

@@ -121,7 +121,7 @@ impl Headers {
         self.find_header_index(name).map(|i| self.headers.remove(i))
     }
 
-    fn find_header(&self, name: &str) -> Option<&HeaderValue> {
+    pub(crate) fn find_header(&self, name: &str) -> Option<&HeaderValue> {
         self.headers
             .iter()
             .find(|value| name.eq_ignore_ascii_case(&value.name))
@@ -305,6 +305,14 @@ impl HeaderValue {
             encoded_value,
         }
     }
+
+    pub(crate) fn get_raw(&self) -> &str {
+        &self.raw_value
+    }
+
+    pub(crate) fn get_encoded(&self) -> &str {
+        &self.encoded_value
+    }
 }
 
 const ENCODING_START_PREFIX: &str = "=?utf-8?b?";